This invention relates to a process for reacting conjugated diolefins with aromatic hydrocarbons.
Many alkenylations of aromatic hydrocarbons by dienes have been described in the literature (for example G. A. Olah, Friedel-Crafts and Related Reactions, volume II/I). The reaction is carried out with homogeneous and heterogeneous acid catalysts and leads predominantly to alkenyl and/or dialkenyl derivatives of aromatic hydrocarbons of the general formula ##STR2## in which Ar is an aryl radical, the radicals R independently are hydrogen or alkyl radicals and n and m are each 1 or 2.
Such substances have hitherto been of only little interest. Frequently, they are only undesired by-products. Because of their high proportion of trans-double bonds, their air-drying properties are poor, and in addition they are relatively highly volatile. Longer-chain telomers (n&gt;2) are usually formed only to a slight extent.
Such products can indeed be obtained by the processes of German Patent Specifications Nos. 1,137,727 and 1,170,932, but they also contain predominantly trans-double bonds as well as a considerable proportion of undesired highly volatile monoalkenylation products (compare also Weber et al, Brennstoff-Chemie 49, 329 et seq. (1968)). They are proposed for uses in modifications of elastomers and thermoplastics, in the field of lubricants and, after hydrogenation, in the field of detergent bases.
When Cr-III halides and alkyl-aluminum halides are used as catalysts according to the process of U.S. Pat. No. 3,373,216, products with a trans content which is relatively lower (35 to 80%) are formed; but they contain only a small proportion of incorporated aromatic radicals.
A process for the manufacture of polymers which contain aromatic hydrocarbons on a polydiene chain (the incorporation probably takes place randomly along the polydiene chain) using a nickel catalyst modified by halogen compounds of norbornene is described in Japanese Laid-Open Specification No. 49 32,985. This procedure leads to products which contain, for example, 0.5 mole of aromatic radicals per 1 mole of diene, and in some cases more than 70% of cis-1,4-double bonds. Nevertheless, this process also has a number of disadvantages. For example, the modifying agents required are not commercially available compounds and the yields are relatively low.